Neuropeptide Y—a novel brain peptide with structural similarities to peptide YY and pancreatic polypeptide

The C-terminal α-amide structure is a characteristic feature of many biologically active peptides1,2. Using a novel chemical method for the detection of peptide amides3, we have isolated two naturally occurring peptides, peptide HI (PHI) and peptide YY (PYY), from extracts of porcine intestine and have shown that these peptide amides represent previously unknown biologically active peptides4. PHI is structurally and biologically similar to vasoactive intestinal peptide (VIP)5 while PYY shows similarities to pancreatic polypeptide (PP)6. Preliminary studies indicated that PHI and PYY may both be present in brain as well as in intestine4. We report here the isolation from brain extracts of a peptide amide that was thought to be PYY. However, we found that the peptide, while having distinct structural and biological similarities to both PYY and PP, is a previously uncharacterized peptide, which we designate neuropeptide Y (NPY).